1) Field of the Invention
The present invention relates to a short fiber and continuous filament composite yarn and a process and apparatus for producing the same.
More particularly, the present invention relates to a short fiber and continuous filament composite yarn having an excellent resilience, an enhanced soft touch, and a uniform spun yarn-like appearance and hand, useful for forming high grade fabrics, and a process and apparatus for producing the same with a high efficiency.
2) Description of the Related Art
It is known that, among the physical properties of fibrous materials, a high resilience and a high softness are usually mutually exclusive, but a limited number of fibrous materials provided with both high resilience and high softness are found among high grade products of a few natural fibers, for example, special silk, wool, and cotton fibers.
Much research has gone into this, but a satisfactory level of both resilience and softness has been achieved in very few natural fiber materials and synthetic fiber materials.
It is considered that the provision of a fiber product provided with both a high resilience and high softness from only one type of fiber is difficult, so most efforts have been directed to the provision of fiber composite products in which two or more types of fiber materials having a different fiber thickness are utilized.
Where two or more types of short fibers are used, the resultant short fiber composite product exhibits an unsatisfactory resilience derived from the short length or crimps, which are made by a compression buckling procedure, of the short fibers.
To solve this problem, attempts have been made to increase the thickness of the short fibers, but in the resultant product, a number of ends of the thick short fibers are extended from the product to the outside, resulting in an itchy or a scratchy feeling when in use. Also, the use of thick short fibers causes an uneven blending of the thick short fibers with the thin short fibers, and accordingly, an uneven draft of the blend of the thick and thin short fibers. Therefore, it is very difficult to provide homogeneous short fiber blended yarn.
Where two or more types of multifilament bundles in which the deniers of individual filaments are different are blended, it is difficult to evenly open the individual filaments in the blend. Also, since the thermal shrinkages of the individual filaments in each bundle are similar to each other, when the multifilaments bundles are blended, the individual filaments having similar thermal shrinkages are bundled with each other to form blocks. Namely, the thick individual filaments and the thin individual filaments in the blend are not uniformly mixed. Usually, the bundles of thick individual filaments are located at peripheral portions of the resultant blended yarn. Also, the thin individual filaments are formed into loops, and thus do not exhibit a resilient touch.
Further, the multifilament bundle-blended yarn exhibits a simple and monotonous appearance, and thus it is difficult to obtain an elegant natural fiber with a spun yarn-like appearance and touch.
Generally, in the preparation of a composite yarn from two or more types of short fibers or continuous filaments having a different thickness, it is difficult to selectively arrange the thick individual short fibers or continuous filaments in a core portion of the resultant composite yarn and the thin individual short fibers or continuous filaments in the peripheral portion of the composite.
To eliminate the above-mentioned disadvantages the following has been attempted:
(1) In a spinning procedure for short fibers, inserting a bundle of continuous filaments into a core portion of the spun yarn to provide a core-spun yarn.
(2) As disclosed in Japanese Unexamined Patent Publication Nos. 59-82424 and 60-2715, draw(draft)-cutting a group of thin individual continuous filaments, and simultaneously, intertwining the resultant short fibers with a group of thick individual continuous filaments.
(3) As disclosed in Japanese Unexamined Patent Publication No. 57-5932, drawing a bundle composed of a group of thick individual continuous filaments having a high ultimate elongation with a group of thin individual continuous filaments having a low ultimate elongation, by a drawing machine or a draw-false twisting machine, while draw-cutting and intertwining the thin continuous filaments with one another.
Nevertheless, the above-mentioned measures did not provide satisfactory composite yarns having a good appearance, satisfactory resilience, and soft touch.
In the above-mentioned attempt (1), the resultant composite yarn had the following disadvantages:
(a) Since the short fibers and the continuous filaments were simply incorporated to and twisted with each other, they were weakly intertwined or entangled with each other, and thus the handling was difficult in the case of a soft twist or moderate twist yarn.
(b) An excessive feed of the short fibers to the continuous filaments was difficult, and thus the resultant composite yarn exhibited an unsatisfactory bulkiness.
(c) The short fibers had to have a small denier. When the denier was 0.8 or less, it became difficult to evenly spin the short fibers.
(d) The procedures were complicated and the productivity low, and therefore, the production cost for the core-spun yarn was too high.
The above-mentioned attempt (2) had the following disadvantages:
(a) Since a bundle of thick continuous filaments was joined with the draw-cut short fibers under a high tension, it was difficult to evenly open the thick continuous filament bundle and firmly intertwine the draw-cut thin short fibers with the thick continuous filaments.
(b) Since the thin continuous filament bundle was draw-cut at room temperature and the thick continuous filament bundle was simply arranged in parallel to the draw-cut short fiber bundle, the ratio in thermal shrinkage of the draw-cut thin short fiber bundle to the thick continuous filament bundle could not be made significantly small, and the covering effect of the thin short fibers on the thick continuous filament bundle was unsatisfactory.
(d) Sometimes the thin continuous filaments are unevenly draw-cut and thus it is difficult to produce a composite yarn having a small yarn count.
The above-mentioned attempt (3) has the following disadvantages:
(a) The draw-cutting ratio is relatively small and thus the draw-cut short fibers sometimes have a relatively large length. Also, since the draw-cutting zone in the conventional drawing machine or draw-false twisting machine is relatively long, the resultant draw-cut short fibers sometimes have a relatively large length of 600 to 700 mm, and the deviation pitch in the fiber length becomes significantly larger than that of natural fibers, and thus the resultant composite yarn exhibits an unnatural appearance.
(b) In a conventional drawing machine in which the thin individual continuous filaments are drawn-cut under a draw-cutting force of several kg per cm of the width of the filament bundle on a draw-cutting roller device in which a pair of nip rollers nip the filament bundle at one nipping point, or one or more draw-cutting apron rollers hold the filament bundle wound around the peripheries thereof, the filament bundle slips on the roller peripheries or is unevenly nipped, and thus is very difficult to be evenly draw-cut.
(c) When the number of individual filaments in the filament bundle is relatively small, the individual filaments are difficult to be uniformly bundled, and thus to be evenly nipped by the nip rollers or evenly held on the apron rollers, due to resistance of air at the free end portions of the draw-cut fibers and an action of air streams accompanying the rotation of the draw-cutting rollers, and therefore, are unevenly draw-cut.
(d) When the filament bundle is heated on a heating roller or plate, the stress of the filament bundle created against a stretch applied thereto becomes small, the heated filament bundle is easily stretched under a small stretch force, and thus unevenly drawn-cut, and the drawn-cut end portions of the resultant short fibers are thermally shrunk and exhibit an uneven dyeing property. Also, the filament bundle is drawn-cut at a high temperature and the drawn-cut short fibers and non-cut continuous filaments are heat-set at this temperature, and thus the difference in thermal shrinkage between the short fibers and the continuous filaments is very small. Therefore the resultant composite yarn does not exhibit a satisfactory bulkiness. Further, when the filament bundle is draw-fake twisted, crimps are created in the individual short fibers and continuous filaments. Since the resultant composite filament yarn is not twisted, the crimps cause an uneven intertwining of the crimped short fibers with the crimped continuous filaments, and therefore, the resultant composite yarn exhibits an uneven bulkiness and a non-uniform appearance. Sometimes the resultant composite yarn undesirably exhibits a similar touch to that of conventional false-twisted textured yarns. Furthermore, as mentioned above, the difference in thermal shrinkage between the thin and thick filaments is reduced by the heat-setting.
Under the above-mentioned circumstances, there is a strong demand for a special composite yarn having both a satisfactory resilience and a natural spun yarn-like soft touch and appearance, from synthetic filaments.